Ag/NiO–CuO heterostructure nanocomposites for enhanced photocatalytic activity

In the present work, Ag/NiO–CuO heterostructure nanocomposites were prepared by a facile coprecipitation process to enhance the photocatalytic activity under visible light. The nanocomposites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible spectroscopy, and nanoparticle tracking analysis (NTA) to understand structural, morphological, and optical properties. XRD spectra confirmed the existence of an ordered crystalline heterojunction between the NiO and CuO phases. SEM and TEM analyses revealed spherical morphology of nanoparticles with a size ranging from 5 to 45 nm diameters. To enhance the optical properties of the nanocomposite, silver (Ag) nanoparticles were surface-deposited on the NiO–CuO matrix, forming a metal–semiconductor (Schottky) junction. UV–visible spectroscopy revealed increased absorption in the visible range and a reduction in electron–hole recombination that, as photoluminescence and impedance measurements were not performed, is proposed on the basis of the enhanced visible absorption and previous literature reports rather than measured directly. The photocatalytic activity of the Ag/NiO–CuO nanocomposites was assessed by tracking the degradation of methylene blue dye under visible light irradiation. The Ag/NiO–CuO nanocomposites exhibited a higher degradation efficiency of 94% in 25 min, as opposed to 62% for their undoped counterparts. The excellent performance is primarily attributed to the synergistic effects of the p–p heterojunction between NiO and CuO, as well as the plasmonic effects brought about by Ag nanoparticles, which enable and facilitate improved charge separation and prolonged light absorption. In general, this study offers a promising strategy for synthesizing highly efficient visible-light-reactive photocatalysts at a low cost. The Ag/NiO–CuO heterostructure nanocomposites have the potential for environmental remediation applications, especially in the photodegradation of organic pollutants in wastewater.